1. Field of the Invention
The invention is directed to an offset printing form and a process for producing such an offset printing form from at least one printing plate which is cut to size and made of metallic material. The starting and ending printing edges of the printing plate are connected with one another so as to form a sleeve.
2. Description of the Prior Art
The prior German Patent Application P 41 40 768 discloses a sleeve-shaped offset printing form which has a continuous circumferential surface without grooves and can be slid onto a form cylinder and positioned on the latter in a working position in exact register in a frictionally locking manner. The sleeve is produced from a commercial printing plate of metallic material, preferably aluminum, which is cut to size and the forward and rear edges of the plate are connected, e.g. welded, with one another so that, apart from a connecting seam, the sleeve has an uninterrupted circumferential surface. Such a sleeve-shaped offset printing form can be used in combination with a form cylinder, e.g. known from the German Patent DE-PS 27 00 118, having no groove or tensioning segment. The printing form can be slid onto the form cylinder by applying compressed air and the form cylinder can also hold the printing form by means of electromagnets when using a sleeve-shaped multimetal plate. Naturally, it must be possible to switch off the magnetic effect during the process of slipping on the printing form.
The great advantage of such sleeve-shaped printing forms is that commercially available offset printing plates and existing plate copies can be used and, in comparison with printing with the use of a tensioning groove, grooveless printing enables an economical manufacture of the cylinder, improved printing quality and higher printing speeds. The connection seam and accordingly the non-printing region are comparatively small.